When transporting communication traffic from many different customers through a switch, router, or other communication equipment, it is highly desirable to ensure that communication traffic from one “misbehaving” customer cannot adversely affect other customers.
It is also generally desirable to allow overbooking of physical media used to transport communication traffic, from a communication network to the end customer, for example. Where many different services are provided on the same physical channel, overbooking the physical media allows use of lower speed and thus lower cost physical media.
If, on an overbooked physical channel, the instantaneous sum of customer traffic happens to be less than the speed of the physical media, all customers can be satisfied. Typically, the rate of any given customer's traffic will vary over time, and peaks in one customer's traffic will be cancelled out by troughs in another customer's traffic, so that the sum of customer traffic is less than the speed of the physical media. Occasionally, however, the instantaneous sum of customer traffic will exceed the speed of the physical media. In this event, a fair way is needed to share the available bandwidth amongst all the competing communication traffic flows.
Providing isolation between customers and/or services when such congestion occurs can be a very complex problem. For example, some communication chip vendors have introduced complex traffic management devices providing per flow isolation for communication traffic that competes for the same physical medium. Many routing/switch vendors have developed their own proprietary solutions to help provide such isolation. Although some existing solutions may allow isolation between 4K physical media, the industry standard System Packet Interface SPI.4 bus interface is still widely used in existing communication equipment but is limited to providing isolation between at most 256 physical media. This limit is associated with the maximum number of hardware backpressure contexts that can be supported by SPI.
Mismatch between isolation capabilities can cause problems when a component having higher isolation capabilities is to be used in existing equipment, and isolation is needed for as many physical media as possible. This type of issue can become even more problematic when a device supporting a higher number of channels receives communication traffic from, but has a lower throughput than, a device supporting the smaller number of channels.
Currently available routers, for example, typically support a few hundred interfaces on a given interface card. Modifying these routers to support thousands of physical interfaces is difficult.
Suppose that it is desired to provide isolation between 4K physical media using a router which has an existing traffic management device that provides isolation between 256 physical media using backpressuring. Although another traffic management device providing the desired 4K isolation could be added to the router and connected to receive communication traffic from the existing traffic management device, the 4K isolation would be lost if traffic becomes congested at the additional traffic management device. The additional traffic management device might be configured to discard incoming communication traffic in this event, or to effectively rely on the backpressure facility of the existing traffic management device to reduce the rate at which that device outputs communication traffic. In either case, the desired level of isolation is lost.
Thus, there remains a need for improved communication traffic isolation and control techniques.